In the context of
smart card
A smart card (SC), chip card, or integrated circuit card (ICC or IC card), is a card used to control access to a resource. It is typically a plastic credit card-sized card with an Embedded system, embedded integrated circuit (IC) chip. Many smart ...
s, an application protocol data unit (APDU) is the communication unit between a
smart card reader and a smart card. The structure of the APDU is defined by
ISO/IEC 7816
ISO/IEC 7816 is an international standard related to electronic identification cards with contacts, especially smart cards, and more recently, contactless mobile devices, managed jointly by the International Organization for Standardization (ISO) ...
-4 ''Organization, security and commands for interchange''.
APDU message command-response pair
There are two categories of APDUs: command APDUs and response APDUs. A command APDU is sent by the reader to the card – it contains a mandatory 4-
byte
The byte is a unit of digital information that most commonly consists of eight bits. Historically, the byte was the number of bits used to encode a single character of text in a computer and for this reason it is the smallest addressable un ...
header (CLA, INS, P1, P2)
and from 0 to 65 535 bytes of data. A response APDU is sent by the card to the reader – it contains from 0 to 65 536 bytes of data, and 2 mandatory status bytes (SW1, SW2).
References
{{reflist
See also
*
Protocol data unit
In telecommunications, a protocol data unit (PDU) is a single unit of information transmitted among peer entities of a computer network. It is composed of protocol-specific control information and user data. In the layered architectures of c ...
External links
Smartcard ISOs, contents Selected list of smartcard APDU commandsSelected list of SW1 SW2 Status bytes
Smart cards
ISO standards
IEC standards